C# Format FileName for Toast Notifications or GUI

Raison D'être 

Ever need to format a filename to fit a certain length to fit a toast notification, label or GUI, but still maximize original filename recognizably?

Description

TrimMidFileNameFormat string extension method that will trim the middle of the filename. It does this by cutting the filename including extension length into specified length. But, it favours splitting the filename into ratio of 1/3rd for leading and 2/3rds of length allocated to last characters before dot file extension. The shrunken filename grows linearly with larger length sizes, until max of leading numbers is reached, in which all growth occurs at end of the filename. This maintains the maximum recognizably of the original filename. 

NOTE! Length includes extension length plus dot. Extensions will not be compressed.

i.e. "SmartFileNameShrinker.exe".TrimMidFileNameFormat(10) outputs "Sm~nker.exe"

Check out the .Net Fiddle which shortens filenames of lengths from 1 to 40.

The impetus, fitting long filename into Windows toast notifications which has a limit of 41 characters if title and body contain some text. 

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using System;using System.Linq; public static class Program { private static string seperator = "~"; //must be single character string, tilde is a valid filename char, may want to use a non-valid char for filenames. private const int leadingnumbers = 5; //number of leading characters to build up to /// <summary> /// Format filename to a length (maxFileLen), by splitting filename into 1/3rd leading and 2/3rds ending until max leadingnumbers is reached. Used for toast nofications less than 41 characters by metadataconsulting.blogspot.com /// </summary> /// <param name="filename"></param> /// <param name="maxFileLen"></param> /// <returns></returns> public static string TrimMidFileNameFormat(this string filename, int maxFileLen) { Console.Write(string.Format("{0,5:###}", maxFileLen)+" "); //remove line when using in your library string ext = filename.GetFileNameExtension(); int extLen = ext.Length; //includes dot in length string filenamelessext = filename.Substring(0, filename.Length - extLen); int filenamelessextLen = filenamelessext.Length; int maxroom = Math.Min(leadingnumbers * 2 - 1, filenamelessextLen); int minLen = 2 + 1 + extLen; //1st char + tilde.length(1) + last char + extLen(min 4) => 7 ie s~p.exe int lastLen = 1 + extLen; // last char + extLen(min 4) ie p.exe if (filename.Length <= maxFileLen) return filename; else if (filename.Length < minLen) return filename; else if (maxFileLen < minLen) //implied && filename.Length > maxFileLen) return filename.Substring(0, 1) + seperator + filename.Substring(filename.Length-lastLen, lastLen); else if (maxFileLen >= minLen && maxFileLen < (maxroom + minLen)) //implied && filename.Length > maxFileLen) { //middle { int room = (maxFileLen - lastLen); int one3rd = (3 + room - 1) / 3; //integer division with round up, old room/3 rounds down. int two3rds = room - one3rd; return filename.Substring(0, one3rd) + seperator + filename.Substring(filename.Length-(two3rds + lastLen), (two3rds + lastLen)); } else if (filename.Length > maxFileLen + leadingnumbers + 1) // > 2 + 1 + extLen (min 4) return filename.Substring(0, leadingnumbers) + seperator + filename.Substring(filename.Length - maxFileLen, maxFileLen); else return filename; } private static Random random = new Random(); //not cryptographically secure public static string RandomString(int length) { const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!@#$%^*-."; return new string(Enumerable.Repeat(chars, length) .Select(s => s[random.Next(s.Length)]).ToArray()); } /// <summary> /// Get filename extension, not ext of . only returns empty string, mirrors Path.GetExtension not try/catch issues by metadataconsulting.blogspot.com /// </summary> /// <param name="s"></param> /// <returns></returns> public static string GetFileNameExtension(this string s) { string ext = ""; int fileExtPos = s.LastIndexOf('.'); if (fileExtPos > s.LastIndexOf('\\')) { ext = s.Substring(fileExtPos, s.Length - fileExtPos); if (ext.Length <= 1) ext = ""; } else ext = ""; return ext; } public static void Main() { string filename = ""; for (int j = 1; j < 41; j++) { filename = RandomString(j) + ".exe"; Console.WriteLine(filename); Console.WriteLine("Length=" + filename.Length); Console.WriteLine(); for (int i = -1; i < filename.Length+3; i++) Console.WriteLine(filename.TrimMidFileNameFormat(i)); //7 min length viable name for shrinked name Console.WriteLine(); } } }